Different situations at construction sites and different milling processes make it often necessary to adapt the milling tool to the specific tasks. For instance, when a specific surface roughness is to be obtained, a milling roller with a special line interval of the milling tools or a different tool equipment will be required. In another application, only lanes of specific widths have to be built, thus requiring a milling roller of a specific working width.
Normally, in such situations, a special milling machine has to be used, or the machine must be equipped with a milling roller adapted to the task. Presently, however, the exchange of the rollers is very bothersome and necessitates special auxiliary tools for the mounting and dismounting of the milling roller.
The adapting of milling rollers to different requirements is known in the state of the art.
DE 40 37 448 A describes a road milling machine wherein the roller body is braced between a fixed bearing carrying the drive housing, and a movable bearing arranged opposite to the fixed bearing. The movable bearing is provided with a centering receiving cone, and the support of the movable bearing can be hydraulically displaced. Further, the movable bearing is braced to the fixed bearing via a tie bar.
The approach known from DE 40 37 448 A requires a complex tensioning mechanism with a tie bar and a operating cylinder above the milling roller.
Described in U.S. Pat. No. 4,704,045 is a milling aggregate which is variable in width by use of various roller segments. According to this approach, the roller segments are connected to each other by a plug connection. In a certain manner, this approach can be considered as a milling roller quick-exchange system but suffers from the following disadvantages:
In this approach, it is disadvantageous that the milling rollers are driven hydrostatically by hydraulic motors arranged on both sides of the milling roller. Further, the connection between the segments is a simple plug connection allowing merely for an insufficient centering of the milling motor.
DE 31 45 713 A describes a milling roller for a road milling machine which is supported and driven by a roller bearing and drive device held by a support frame, wherein the milling roller comprises a cylindrical base body. Arranged on one end of the one-sided milling roller are the drive unit of the roller bearing and drive device as well as an annular shoulder supporting the milling tube mounted from the other end. On the side opposite to the drive unit, a holding flange is arranged for fixing the milling tube. According to this concept, the milling roller is provided with a hydrostatic drive which due to its system-inherent disadvantages, e.g. low efficiency, is nowadays hardly used any more in road milling. A further disadvantage of this approach resides in that the milling tubes have to be axially fixed by means of annular shoulders so that the fastening elements are located in the region of the strongest contamination.
U.S. Pat. No. 4,720,207 describes milling tube segments mounted on a roller base body. In this concept, a corner ring segment is first applied on one side. Then the milling tube segments are attached thereon by screw-fitting, with the thread connection arranged within the segments. Disadvantages reside in the considerable expenditure for the screw connections and in that, due to the constant diameter of the base body, the milling depth is restricted when a planetary gear is integrated into the base body.
A different approach wherein particularly the milling depth is not restricted, is described in U.S. Pat. No. 5,505,598. According to this approach, the milling roller tube having the segments with the milling tools mounted thereon, has a stepped shape. The reason therefor is that the transmission required for a mechanical milling roller drive is integrated into the rotor. The planetary gear is arranged on the side opposite the belt drive disk and is driven by a drive shaft guided through the milling shaft.
This transmission arrangement is required to allow for a flush milling. In the region of the roller transmission, the diameter of the milling shaft is adapted corresponding to the constructional volume of the transmission. The rest of the region will then be available for the mounting of segments with the milling tools.
In this approach, it is disadvantageous that different milling processes, such as normal and fine milling, cannot be performed without exchanging the milling rotor.
Present milling rollers and inventions for adapting the milling tools to different applications are focused merely on the adapting of the milling rotor to the respective situation at the construction site.
A problem in the above mentioned state of the art normally resides in that the fastening elements for fixing the milling element to the base body are provided in the surface region of the cylindrical milling tool. Exactly this region, however, is subjected to massive contamination so that the exchange of the milling tube is rendered considerably difficult.